Adjustable probe for high-frequency electrical devices



April 1953 J. R. BIRD ETAL 2,636,084

ADJUSTABLE PROBE FOR HIGH-FREQUENCY ELECTRICAL DEVICES Original Filed June 16, 1949 2 SHEETS-SHEET 2 I17 I as I16, 8 U5 8 I1 I /Z5 [56 z: 2 I I52 I40 7 I42 Llamas .B/ro

Patented Apr. 21, 1953 ADJUSTABLE PROBE FOR HIGH-FRE- QUENCY ELECTRICAL DEVICES James B. Bird, Chagrin Falls, and Joseph A.

Bilski, Cleveland, Ohio, assignors to Bird Electronic Corporation, Cleveland, Ohio, a corporation of Ohio Original application June 16, 1949, Serial No.

99,474. Divided and this application November 26, 1952, Serial No. 322,767

6 Claims. 1

This invention relates to electrical measuring and detecting devices for use in high frequency electrical apparatus. Such a device or measuring instrument is disclosed in copending application ior United States Patent Serial No. 99,474 filed June 16, 1949. The present invention is con cerned with probes or coupling devices used in voltage dividers and the like for instruments of the character referred to and employed for detecting or sampling wave energy in tubular conductors.

Improvement of the physical structure and arrangement of parts in high frequency electrical detecting devices and in voltage and power measuring instruments is a principal objective of the present invention. It is sought to provide a generally improved probe and voltage divider assembly for use in such electrical detecting and mean uring instruments, more specifically to provide an adjustable probe for a capacitance voltage divider or current sampler for high frequency use of the type in which the components are grouped in a compact assembly for attachment as a unit to a high frequency device.

Another object is to provide an adjustable probe as one component of an assembly, preferably a tree structure arranged within a chambered metal body which shields, supports, and protects the tree components.

Other objects and advantages pertaining to certain features of construction and combinationsand arrangements of parts obtaining simplicity and economy are set forth in the following detailed description. This description is made in connection with the accompanying drawings forming a part of the specification.

In the drawings:

Figure 1 is a vertical sectional detail showing the adjustable probe of the present invention in a voltage divider or current pick-up assembly mounted on the transition or connector section of a coaxial line terminating unit;

Fig. 2 is a diagrammatic representation of a suitable electrical measurin device or wattmeter incorporating the probe assembly of the present invention;

Fig. 3 is an enlarged sectional detail with parts removed, taken substantially along the line indicated at 3 -3 of Fig. 1; and

Fig, 4 is an enlarged elevational detail partly diagrammatic, partly in section and with parts broken away and removed, showing the mounted voltage divider probe assembly connected to the current measuring device or galvanometer.

The present invention is concerned with the construction and arrangement of an adjustable probe unit of a voltage divider assembly mounted, say, on the tapered transition section of a coaxial line terminating unit designated at B. The complete instrument combination is more fully disclosed in the copending application referred to. Other combinations and uses of the present probe are, of course, contemplated. Power measurement is obtained and visually or otherwise indicated by means of a direct current or voltage measuring instrument such as a conventional galvanometer G.

The coaxial line unit B includes an outer tapered conductor or horn (not shown) attached at its large diameter end to a tapered or frustoconical connector I. In making connections between permanently joined metal parts of the apparatus, soldering, brazing or welding is employed, using conventional techniques,

At its small diameter end the connector i is formed with a tubular cylindrical portion I5 which receives a turned brass fitting 15. A metal sleeve, a fragment of which is shown at I I, has a collar is welded or braced on one end. Screws 20 (Fig. 5) extend through the collar l9 and are threaded into the fitting IS. The joint is made fluid-tight as by a resilient O-ring 2| compressed between the end of the sleeve I! and a flanged retainer ring 22. The circular flange on the retainer 22 engages one end of circular dielectric plug l8.

Extending longitudinally through the outer conductor of the line is an inner conductor assembly which includes a ceramic core (not shown) coated with a conductive carbon film, One end of the coated tube is received within a hollow cylindrical portion on the large diameter end of a tapered metal connector 21. The tapered connector 21 is formed or fitted at its small diameter end with a cylindrical rod 28 that is embraced and supported by the dielectric plug l8. The end of the rod 28 is split axially and bored out or otherwise formed for connection to the center conductor of a conventional coaxial electrical line. Threads on the tubular sleeve I! receive the internally threaded collar of the coaxial line so that the outer conductor of such line makes electrical contact with the sleeve. Thus power to be absorbed or measured by the present device can be fed into the coaxial line unit B.

Difficulty has been encountered heretofore in obtaining accurate readings of voltages prevailing across coaxial lines and devices. Sampling of high frequency potentials across or at the entering ends of coaxial line devices has, however, been obtained by the use of capacitance voltage dividers and the present sampler D incorporates-v a number; of improvements in such devices. It embodies a compact capacitance volt age divider one component or which is the adjust able probe of the present invention. A chame bered or hollow body It, formed of, brass. or simie lar conductive metal, is contoured; on. one side. to conform to the outer surface of the connector '5 and is attached to the connector: as DYSDIQQILP- ing or brazing. The body is iormed witha-cen tral chamber H which communicates with-the annular space between the center connector 2? and the tubular comiector i through a; lateral opening in the body and an. aligned opening. T2 formed in the connector.

Supported within the body is a tree structure comprising a conductive metal stem- 13 having a number of angularly disposed radial branches. The stem" and branches are-insulatedfrom the body 10- and the stem is" centered or:

axially disposed in-thechamber T i-- which cham:-

ber may be formed as-by drillingLtopr-ovide: the. One end of the stem is is adjustable in: length and comprisesa metal probe 'ld which istelescoped into t'he end of the stem body and projects intothrough the opening TZ into the-space between: the inner and outercomponents of the oo;-

different diameters desired.

axial line. This probe-and the inner or center-s conductor of the coaxial line B comprise an adjustable or variable capacitor 01'" condenser C The probe is circular in section and has one end? l5 threaded and screwedinto internal threads: formed in an axial bore' within one end of'the' stem 13. The threaded endof the probeii's resilient and expansible; being axially slotted as indicated at 16- (Fig. 1) and spread slig-htly prior to assembly as is the resilient and expansible l slotted end of thestem 7'3 in wliich theprobe is received. 'Ihethreaded parts" are thus-frictionally restrained against relative turning and the probe 74'- is' retained-many desired position of axial adjustmenta It' isapparent that the relatively thin sectioned l endportions" 68 and of the stem and: oftheprobe-respectively. are of greater yieldability; being relatively resilient; and more readily conformto theparts-With; which they are telescoped than wouldbe-the= case with corresponding parts of relatively thick section; Such turning adjustment'isefiected asby means of a hex ended rodpassedax-ially-intothe-stem it through a bore H and received in-a matinghex socket 18 'formed in the; body of;' the probe i l. The body it? is formed with" an access opening into the chamber H alignedwiththe" stembore 71, the; body opening being'normally sealed by a threaded" metal plug-- I48.

The ends of the probe-and the-stem: are re ceived and enclosedine-cylindricalflanged cup 8t formed of a relatively tifi insulating material such as polytetrafluoroethylene; This" cup extends through passage" 8 l inthe' connector? and into the annular space between the-coaxial line components. A threaded" counterbore at the inner end' of the bodypassage 31 receivesathreaded'washerv 8% which compresses a washer 83 against the flanged end of the cup-dil te hold the cup in place and to provide a? fluid-tight seal. The insulating cup 89 thus provides a sealed closure for the passage oropening into the chamber H- of the probe andcrystal assembly D, preventing'liquiddielectric. from entering the chamber-from the line structureB':

. lar. material.

1 ceives' a threaded. metal, plugv 1 sleeve.

Another branch of the tree structure is a cylindrical rod condenser element 85 disposed at a right angle to the stem l3 and which extends laterallythroughv a radiali opening; 86 in the body 10. TherodB5 is secured inza. transverse hole 81 drilled through the stem 13. Outer condenser element 88 is received over the rod 85 and. constitutes therewith the capacitor 0-2. The" tube. element 83 is formed with a reduced diameter end 89 press fitted into the radial passage: 86.-and soldered.

Ceramic: sleeve: 9 0 locates and supports the treest'ructure within the conductive metal body 10 and is form'ed of electrical porcelain or simi- A. reduced diameter portion on the. end. of yieldable polytetrafluoroethylene sleeve'9il isz-received within circular bore 92 of the capacitor cap 88 and annular shoulder 93 ofthe insulating sleeve seats against the end of the capacitor cap 88 to locate the parts in assembly;v

Across-the.body 'chambcr Hxirom the: capacitor 0-2; isiarectifier: assemb'ly thatz'includes: a tubular;

retainer-or" sleeve 95 whichhasa threaded: sen"- tralportion; received. in a.- threaded: radial passagez. 96 aligned: with; the capacitor passage 85L. The: crystal :retainer 9:5; is formed. with a. tapered or; frustot-conical seat; 9?]; which is: engaged by the matching face: of: ayieldable: dielectric washer'efii The gasket orwashen'liiiis received about a tubular end portion 99 of the rod- 85' In, one endzor: the tube a threaded. base; plug i 93 holds an: adj usta'ble;brasssrodaonwhich: is mounted a current; rectifying: crystal I [3.132

The; otherend ofxthe: insulating: tube 32. re-

lllr'l having a rounded-end: l flfirrec'eived ,slidinglyin thetubular end 99 of; the: rod, 85;, the: tube being: slotted axially at "061 to. grip" theplug resiliently. A spring-like whisker wire: lflii-securedin theplug I07 makes point: contact. with; the crystal. lil l.

The-cavity in" the tube 102" is? filledwith wax.

The: crystal unit me is: held: inrplace byra metal cap; I I0 having az..thin=. edge- H I flanged over an annular rib on thersleeve: 1M;

- sleeve i01 seats against the. endi-of-counterbore I I 4 in t'he' retainer" sleeve=95 to locate the crystal holding sleeve in the assembly. A rubbero-ring H6= is" received about the crystal holding sleeve and the-locatingrib- H5; The inner end of the crystal holding sleeve I01 is axially slotted at ill to provide a plurality of axial tines which frictionallyengage thewallsof' the retaining sleeve 9'5" to hold" the crystal unit within the A- linkxchain H8 is connected between the cap Hi! and to the body 70.

A third branch 7 of the" tree structure comprises aresistor'R; of" the insulated" metalized type. which is connected in series. between the stem i Bland one -terminal ofthagaivanometer G. The

other terminal of the galvanometer is connected to' thee'body Til of 'the.-.vol'tagedivider or crystal cartridge assemblyrDl Wire-I23 from one end of the'resistorR i'si connected tothe stem- 73" and wire [-24" from the-other end is connected to a Rubber Caring I12 i'siinterposed; between the insideend'oi" the metal terminal plug I supported by body I26 of phenolic resin held in externally threaded tubular fitting I21 screwed into a radial opening in the body 10. The inner end of the passage through the fitting I 21 is counter-bored to receive a button capacitor 0-3 which makes electrical connection with the walls of the counterbore in the metal tube I21 through a metal ring I32.

Over the outer end of the tubular fitting I21 is received a metal connector fitting I33 having a threaded metal collar I34 which engages the threads on the tubular fitting iZ'I. A spring I35 disposed in the upper end of the fitting I23 is insulated from the "walls of the fitting by a plastic disc I 36 and a dielectric cup I37. A rubber O-ring I38 embraces the end of the plastic cup I31 and is interposed between the side face of the fitting I33 and the end face of the tubular fitting I21 to provide a dust and moisture proof seal.

The galvanometer G is connected by means of a flexible cable comprising a central wire or conductor I40 and a flexible metal sheath MI. The center conductor of the coaxial cable is surrounded by insulating tube I42 and a protective insulating sheath I43 surrounds the woven concluctor MI. The center conductor I40 and the tubular insulation I42 are received in a bore I45 formed in the swivel end fitting I33. A threaded ferrule I46 surrounds the flexible cable and compresses an insulating plastic jam Washer I49 and a rounded end metal jam Washer I50 in the tapered portion of the counterbore. The chamber II, which is formed with an opening through the end of the body I0, is closed as by a threaded metal plug I48.

The voltage drop or potential difference across the input end of the load B, between the center tapered connector 21 and the surrounding or outer tapered connector I, is divided between the capacitors C-I and C2 inversely proportional to their capacitances. Capacitance C-I, comprising the inner connector 21 and the probe I4, is relatively small with respect to the coaxial capacitance C-Z. Accordingly the voltage drop across C2 is a small fraction or sample of the total voltage impressed upon the coaxial line B.

The action of the crystal and other circuit elements described herein is to produce in the galvanometer G a small direct current proportional to the high frequency voltage across the coaxial resistor device D. The galvanometer, by suitable calibration of its dial, thus indicates directly the high frequency power being absorbed.

In accordance with the patent statutes the principles of the present invention may be utilized in various ways, numerous modifications and alterations being contemplated, substitution of parts and changes in construction being resorted to as desired, it being understood that the particular apparatus and combination shown in the drawings and described above are given merely for purposes of explanation and illustration without intending to limit the scope of the claims to the specific details disclosed.

What we claim and desire to secure by Letters Patent of the United States is:

1. A probe structure for use in combination with a high frequency electrical transmission line having an opening, said structure comprising a stem member and means for mounting the stem member on the line in insulated relation, a probe member mounted on one end of the stem member, the members being received one within the other in the provision of a telescopical con- 6 nection, said connection including interfitting threads formed on the members for relative axial adjustment of the probe member in varying the position of the latter relative to the line opening, said telescopical connection also including axially spaced portions located one at said one end of the stem member and another at one end of the probe member axially spaced along the stem member from said one end of the latter, one of the members at each of said axially spaced portions of the telescopical connection being resilient and radially yieldable and being sprung against the other member in the provision of frictional restraint against turning and yielding contact between the members at said one end of the stem member and at said one end of the probe member, and the resilient and radially yieldable member at one of the axially spaced portions being formed with threads to constitute an element of the interfitting threads of the connection.

2. A probe structure for use in combination with a high frequency electrical transmission line having an opening, said structure comprising a stem member and means for mounting the stem member on the line in insulated relation, a probe member having a telescopical connection with the stem member, the stem and probe members being formed with interfitting threads along part of the telescopical connection for axial adjustment of the probe member relative to the stem member upon relative turning of the members in varying the position of the probe member relative to the line opening, one of the members having at one part of the telescopical connection a resilient and radially yieldable end portion sprun against the other of the members, and at another part of the telescopical connection axially spaced along the probe member from said first mentioned part of the telescopical connection one of the members having a resilient and radially yieldable end portion sprung against the other of the members, one of the said resilient and radially yieldable end portions being formed with threads to constitute an element of the said threaded part of the telescopical connection.

3. A probe structure for use in combination with a high frequency lectrical transmission line having an opening, said structure comprising a stem member and means for mountin the stem member on the line in insulated relation, a probe member in telescopical relation to the stem member, the said stem and probe members having portions formed with interfitting threads to effect axial adjustment of the probe member relative to the stem member upon relative turning of the members and having other portions formed with smooth cylindrically curved surfaces in sliding telescopical engagement with one another, the smooth surfaced portion of one of the member being resilient and radially yieldable, and the threaded portion of one of the members also being resilient and radially yieldable in the provision of frictional restraint against turning and yielding contact between the members at both the smooth surfaced portions and the threaded portions.

4. A probe structure for use in combination with a high frequency electrical transmission line having an opening, said structure comprising an elongated tubular stem member and means for mounting the stem member on the line in insulated relation, a probe member in telescopical relation to the stem member, said stem and probe members having portions formed with interfitting threads to eifect axial adjustment of 2, scenes.

7t the; probe: member relative-; to the. stem. member. upon. relative; turning; of. the; members and hav ing other portions;v formed with; smooth cylindrioally curved surfaces in sliding telescopical engagement. with one another, the. smooth surfaced portion of. one. of. the members. being. resilient and. radiallyyieldabla, the threaded. pol.- tion; of one of the; members; also being. resilient and: radially. yielda-ble; in th provision of trio.- tional restraintlagainstlturning.andyieldingcontact between.. the, members. at. both. the. smooth. surfaced portionsa-ndv thathreaded portions, and,

the probe member. being accessible. through; the tubular. stem..member. for; engagement. by a. turn.- ing. tool; in. adjusting. the. position of the probe memben.

5.. A probe. structure. for. use. in. combination with. a. high frequency electrical transmission line having, anopening, said. structure comprisingv an elongated. tubular stem memberv and means for mounting tbestemmember on the line in insulatedrelation, aprobe member mounted. on one end. of." the. stem. membenpthe members being received one Within the: other inthe provision of a telescopicalconnection,.said connection including;v interfitting, threads. formed on. the members for. relative axial. adjustment of the probe member upon relativev turningofthe members in varying the. position of the probe member relative to the line opening,. said telescopical connection alsov including axially. spaced portions located one at said'one end'of thest'em' member and another at one end of the probe member axially spaced along the stemmember from said one end of the latter; one of'them'embersateach of said axially spacedportions" ofithe telescopical connection being. resilient. and radially yieldable and being sprung against the othermember'in' the provision of frictional restraint against turning and yielding contact between the members'at'said one end'of' the" stem memberand at said one end of the probe member; the resilient and radially yieldable member, at one of the axially spaced portions beingformed with threads to constitute an. elementof theinterfitting threads oLthe con.-

nection and: the; probe, member; being. accessible. through the tubular. stem. member, for. engagement. byaturning. toolin adjusting the. position 1 of the. probe member..

6. A probe structure. for. use. in. combination. with a highfreqnency electrical. transmission line. having an. opening, .saidstructure comprising. a

stem member and means for mounting the stem. member on theline ininsulated relation, aprobe member mounted on. one endv of the stem member, one ofthe members having an. axial-circular sectioned recess opening: through one. end. thereof.

and including coaxial recess. portions of. different diam'eterscontinuous with one. ancthenthe other of. the members being receivedwithin the recess of one-member. in theprovision of a telescopical. connection and. having. portions complemental to the said recess. portions in the provision ofjmutually contacting relatively slidable surfaces on the .members, one. of the. recess portions and, the portionof; the other member. oomplementalthereto being formed With. interfitting threads for relative axial. adjustment of. the probe member in varying the. position: of the latter relative to the line opening, and said telescopic-a1 connection.

also including axially spaced portions located at the said. different diameter recess portions, in each 01. said axially spaced portions one of the members being resilient and radially. yieldable:

and. being sprungagainst the other of the members.

JAMES RBIRD. JOSEPI-IiA. BILSKI.

References Cited in-the file of this patent UNITED STATES PATENTS Number Name; Date.

2,427,752 Strempelet a1 Sept. 23; 194%? 2432;097 Hewitt; Dec; 9, 19%? 2,575,799." D'oherty- Nov. 20, 1951 2,605,459 Cook; July 29; I952 

